July 19, 1918. THE COLLIERY GUARDIAN. 127 CARBOCOAL.* By C. T. Malcolmson. Experiment^ conducted during the past three years at Irvington, N.J., under the direction of Mr. C. H. Smith, have resulted in the perfection of a process for the manufacture of smokeless fuel from high volatile coals and for the recovery and refinement of the coal tar products derived therefrom. The low temperature distillation of coal has interested investigators for many years. Sporadic attempts have been made to solve the mechanical problems, but until the Smith process was developed they were not carried to conclusions of economic value. The present coal shortage and the increasing demand for smokeless fuels make this subject one of timely interest. Description of Plant. The following equipment was installed and operated during the experimental period: Four horizontal and two vertical units of commercial size for the low •temperature distillation of the coal; two vertical, two horizontal, and two inclined benches for distilla- tion of the briquettes at medium and higher tempera- tures ; presses and auxiliary equipment necessary for making briquettes; and a complete by-product recovery and tar-refining plant. This commercial equipment is provided with gas and electric meters, pyrometers and other apparatus for recording accu- rately the results of all experiments. There is, in addition to the commercial equipment, a complete chemical laboratory with distillation and recovery apparatus, including facilities for refining and crack- ing the tar and measuring the yields and calorific value of the gas. Description of Process. The products comprise a briquette fuel (“ Car- bocoal ”); a yield of tar more than double that ob- tained in the ordinary by-product coking process; ammonium sulphate in excess of that normally re- covered in the ordinary by-product coking process, and gas in amount approximately 9,000 cu. ft. per ton of coal carbonised. This gas is at present used in the process. The essential features of the Smith process are the two distillations carried on at different temperatures, first of the raw coal and second of the raw briquettes. The raw coal, after being crushed, is distilled at a relatively low temperature, 850 degs. to 900 degs. Fahr., and the volatile contents are thereby reduced to the desired point. The result of this first distilla- tion is a large yield of gas and tar, and a product rich in carbon, termed semi-carbocoal. The semi- carbocoal is next mixed with a certain proportion of pitch obtained from the tar produced in the process, and this mixture is briquetted. The briquettes are then subjected to an additional distillation at a higher temperature, approximately 1,800 degs. Fahr., re- sulting in the production of carbocoal, the recovery of additional tar and gas, and a substantial yield of ammonium sulphate. The characteristic feature of the primary distilla- tion is that it is continuous, and that the coal is constantly agitated and mixed during the entire operation. This is accomplished by a twin set of paddles, which also advance the charge through the retort. By this means all portions of the charge are uniformly distilled, and by controlling the speed at which the charge moves through the retort, the dis- tillation may be arrested at any desired stage. As only a partial carbonisation is permitted in the primary distillation, the hard metallic cells charac- teristic of coke are avoided. The period of distillation is 1 to 2 hours, and the continuous retort has a carbonising capacity of one ton of coal per hour. In the subsequent distillation of the briquettes, all evidence of the pitch as a separate ingredient dis- appears. There is a marked shrinkage in the volume of the briquette, with a corresponding increase in density, but no distortion of its shape. This dis- tillation requires 4 to 5 hours, and is performed in an inclined, self-charging and self-discharging bench. The carbocoal represents more than 72 per cent, of the weight of the raw coal, the exact percentage depending upon the volatile content of the latter. Characteristics of Carbocoal. Carbocoal is dense, dustless, clean, uniform in size and quality, and can be readily handled and trans- ported long distances without disintegration. It is greyish black in colour, sightly resembling coke, but its density more nearly approaches that of anthracite coal. The briquette can be made in any size, from 1 oz. to 5 oz., the larger sizes being better suited to locomotive purposes, and the smaller sizes for domestic use. Heretofore devolatilised fuels, such as coke, have not attained the high rates of combustion desired for locomotive, marine and general steam purposes, and their greater displacement has operated against their general use where transportation cost or stowage space has been an important factor. Carbocoal overcomes these objections. It is actually a relatively soft but tough form of carbon, readily attacked by oxygen in combustion, and for this reason requires much less draught than other high carbon fuel. Carbocoal for Steam Purposes. Carbocoal has been tested by the Long Island Rail- road; by the Pennsylvania Railroad at its testing plant at Altoona; by the Carolina, Clinchfield and Ohio Railroad; and by the United States Navy. These tests have demonstrated that the fuel is smoke- less ; that it will evaporate from 8'5 lb. of water at a combustion rate of 100 lb. per sq. ft. of grate sur- face per hour to 12-8 lb. of water at combustion rate of 27 lb. per sq. ft. of grate surface per hour, from and at 212 degs. Fahr, per lb. of fuel fired, and that it requires no greater draught than bituminous coal. * From a paper presented to the American Institute of Mining Engineers. A maximum combustion rate of 166 lb. per sq. ft. of grate surface per hour has been reached for a short period. Carbocoal has been found particularly suitable for marine and locomotive service, stationary boilers, domestic uses, kilns, drying and roasting ovens, and metallurgical furnaces and gas producers. Carbocoal as a Domestic Fuel. Carbocoal has been subjected to practical tests in household use for over a year, and fulfils all require- ments of burning satisfactorily without change of furnace or grates, and responding readily to changes in draught. The uniformity of oombustion, absence of fines, even distribution of ash, and absence of clinker as compared with the coal from which it is made, are additional characteristics in favour of this fuel. Tests have demonstrated that carbocoal can be banked satisfactorily over night, requiring no more attention, and with no greater consumption, than anthracite. Comparison with Other Briquettes. Carbocoal is compressed into briquette form to obtain maximum density, to minimise transportation costs and the losses incident to handling, and to secure the efficiency of combustion resulting from uniformity of size. It is an entirely distinct product from the ordinary briquettes of bituminous and anthracite coals, and differs from the original coal in chemical and physical properties. The briquettes contain no binding material to soften or disintegrate in the fire. Analysis of Carbocoal. The amount of ash and sulphur in the carbocoal depends upon the characteristics of the coal from which it is made. The summarised proximate analyses of carbocoal, manufactured from 25 different coals at the Irvington plant, are shown in Table 1. Table 1.—Analyses of Carbocoal. From run of m i ne, From washed coal, per cent. per cent. Moisture ......... 1’00 to 3'00 ... TOO to 3'00 Vol»tile matter... 0*75 to 3*50 ... 0*75 to 3*50 Fixed carbon ..... 82*00 to 88*i'O . 85’00 to 90*00 Ash............... 8*50 to 12*00 ... 7*00 to 10*00 Sulphur .......... 0*5 to 1’50 ... 0*6 to 1'50 The percentage of by-products recovered from clean coal is greater than that recovered from high ash coals; therefore the careful preparation of the raw coal by washing or other means is profitable. Tar and Its Products. The total yield of tar by the carbocoal process is large, coal containing 35 per cent, volatile combustible producing more than 30 gals, of water-free tar per short ton. The tar products obtained at the low temperature used differ in nature from those obtained in other processes where high temperatures are used. At the lower temperature there is an abundance of tar vapours, and a relatively small yield of gas of high illuminating value. At the higher temperature these primary products are split up, with a consequent increase in the gas yield and a corresponding decrease in its illuminating value and in the amount of tar vapours recovered. There is also an increase in the percentage of residuals, the pitch increasing from 30 per cent, in the low temperature distillation to 64 per cent, or more when high temperatures are used. The tar obtained in the primary distillation of the coal has a specific gravity of 1*00 to 1*06. It con- tains a large percentage of light solvent oils, tar acids and cresols, but very little carbolic acid and no naphthalene or anthracene. The free carbon content is low. The light oils contain appreciable quantities of naphthenes, pentane, hexane, hexahydro benzenes, and also hydrocarbons of the paraffin series, which make these oils valuable as a substitute for gasolene. A satisfactory method of removing the paraffin and aromatic portions of the light oil has been developed, so that c.p. benzol and toluol can now be obtained by this process. During the low temperature distilla- tion period, 20 to 28 gals, of tar, including the light oil obtained from the stripping of the gas, are re- covered, the exact amount depending upon the volatile content of the coal. This low temperature tar con- tains approximately 30 per cent, of pitch and 70 per cent, of tar oils, as compared with 50 to 60 per cent, of pitch and 40 to 50 per cent, of oil products contained in ordinary gas house and coke oven tar. In the second or high temperature distillation 5 to 6 gals, of tar are added to the &bove yield. This tar is heavier than that obtained from the first distillation and is similar to coke-oven tar. Table 2 compares the tars and light oils obtained in the production of carbocoal with those obtained in the ordinary by-product coking processes. Table 2.—Recovery of Liquid Products per Ton of Raw Coal. Carbocoal, Carbocoal, first second distillation distillation Distilla- tion tempera- By product coke oven ture, (------A-------> (--------*-----' t-------A----\ degs. F. Gals. P.c. Gals. P.c. Gals. P.c. Lightoil... 0-170. ..0*27... 3*47... 1*58... 6 60...0W... 0*05 Middle oil 170-230...0*44 .. 5*85... 3*29... 13*70...0*036... 0*60 Creosote oil 230-270...0*78... 10 37 .. 3*11... 12*95...0*126... 2*10 Heavy oil ..270-360...1*26... 16 81... 8*88... 37*00...2*485... 41*42 Pitch........... — .. 4 66... 62T8 .. 6*90 . 28*75...3*290... 54*83 Loss ............. — ...0*09... 1 32... 0*24... 1 00...0*060... 1*00 Totals ... — ...7’50... 100*00...24*00 100*00 . 6*000... 100*00 In addition to the above yield of tar, 2 to 3 gals, of light oil are obtained, in both the by-product coke oven and the carbocoal process, by stripping the gas. This yield depends upon the characteristics of the coal carbonised. Approximately 30 per cent, of the fractions from 170 degs. to 360 degs. Fahr, in the carbocoal process are tar acids; the remainder of the fractions are neutral oils. The value of the products from the distillation of tar depends, of course, on the extent to which the tar is refined. The fractionation and subsequent treatment of the tar oils, which is a part of this process, give the products shown in Table 3 in carbonising 1,000 tons of coal; the figures are based upon data obtained from carbonising run-of-mine coal from Clinchfield, Va. Table 3. 1. Carbocoal ...*..........................725 tons. Analysis. Raw coal. Carbocoal. Moisture................ 0*72 .. 1*84 Volatile matter ....... 35*01 2*75 Fixed carbon........... 57*23 85*64 Ash ..................... 7 04 ... 9*77 100*00 ... 100*00 Sulphur ................ 0’63 ... 0*52 2. Sulphate of ammonia..........20,000 to 25,000 lb. 3. Other nitrogen products, prin- cipally pyridine bases ..... 2,000 to 4,000 oz. 4. Motor spirit ................ 1,800 to 2,200 gals. (or c. p. benzol 250 gals. c. p. toluol 500 gals., motor spirits 1,000 gals.) 5. Crude tar acids, principally cresylic acids....................... ... 4,040 gals. 6. Water-white naphthas................ 3,500 gals. 7. Creosote oil ....................... 5,450 gals. 8. Heavy creos te oil ................. 4,660 gals. Other products, used in process : 9. Pitch ............................. 10,000 gals. 10. Gas, of 530 B.Th.u., approximately ...9,000,000 cu. ft. Pitch is always an element of questionable value in tar distillation. The Smith process, however, utilises all its pitch for briquetting the semi-carbocoal pro- duced by the first distillation. Moreover, the valu- able portions of this pitch are recovered in the tar and gas resulting from the second distillation. It is therefore noteworthy that all the tar products re- covered by this process are oil derivatives. Ammonium Sulphate. The primary distillation of the raw coal gives only a small yield of ammonium sulphate. The secondary distillation of the raw briquettes, however, brings the amount up to approximately 21 lb. per short ton of raw coal carbonised. Gas. In the primary distillation, from 5,000 to 6,000 cu. ft. of gas per short ton of coal is recovered. This has a heating value of 650 to 700 B.Th.U. per cu. ft. The distillation of the briquettes yields also about 4,000 cu. ft. of gas of 350 to 400 B.Th.U. per cu. ft. The process in its present stage of development uses all of the gas recovered from both distillations. Suitable Coals. The carbocoal process has been applied to both coking and non-coking coals. It has been found to work satisfactorily with the non-coking coals of Utah, Washington, and Illinois, and the coking coals of Pennsylvania, Virginia, West Virginia, Tennessee, and British Columbia. Through the application of this process many black lignites or sub-bituminous coals may be converted into a fuel of higher economic value. By-Product Gas Producers. Another application of the Smith process equal in importance to the manufacture of carbocoal is the adaptability of a certain part of the process to the production of electric power. The carbon residue, or semi-carbocoal, the residue of the primary distilla- tion, is a non-caking fuel, practically tar free. Although representing 72 per cent, of the original coal by weight, it contains nearly all the nitrogen originally in the coal. It therefore provides an ideal fuel of high nitrogen content for the by-product pro- ducer. A combination of this kind would recover the maximum percentage of tar and ammonia products, with a large yield of low B.Th.U. gas, which can be burned satisfactorily under steam boilers, and thus produce cheap power. Welsh Fuel Controller.—Mr. J. I. Thomas, of the Cam- brian Railway headquarters staff, Oswestry, has been “ loaned ” to the Board of Trade to administer the Fuel and Lighting Order in the six counties of North Wales. Mr. Thomas has had 46 years’ experience of railway work, and has held appointments at Carmarthen, Cardiff and Sheffield. Patents in Enemy Countries.—The Board of Trade noti- fies that it has revoked the general licences of December 7, 1915, and September 5, 1917, under which, subject to certain conditions, the payment was permitted of fees, etc., due in enemy countries in respect of the grant, regis- tration or renewal of patents, designs and trade marks, and also the payment in His Majesty’s dominions and Allied territory on behalf of enemies of similar fees, etc., in respect of such industrial property. All such payments are consequently prohibited in future. Colliery Enginemen’s Wages.—The Prime Minister re- ceived at 10, Downing-street on Friday a deputation from the National Council of Mine Workers other than miners, representing over 10,000 enginemen, stokers, and crafts- men employed in collieries throughout the kingdom, with whom he discussed the question of wages and other matters which had been the subject of negotiation with the Coal Controller. A deadlock threatening a national stoppage having arisen owing to the rejection of the offer of an advance of Is. 6d. a day to workers over 16 years of age and 9d. a day to youths, the intervention of the Prime Minister was sought with a view to securing an amicable settlement. The men asked for a further advance in wages of 25 per cent., together with minimum rates, the aboli- tion of non-union labour, and an eight-hour day for all pit workers. The Prime Minister, having heard the men’s case, made a certain offer, and left the conference to keep another appointment, the Coal Controller (Sir Guy Cal- throp) and Sir Richard Redmayne discussing the matters further with the deputation. No decision was reached, and it was arranged to hold a further conference with the Coal Controller. The deputation had an interview with the Coal Controller on Wednesday, and pressed the claim for a proportionate overtime payment for each shift on which overtime had to be worked. The Coal Controller asked for an adjournment, so that he might communicate with the colliery owners on the points raised by the work- men, and promised to meet the men’s representatives within fourteen days, and give them a definite decision. The National Council agreed to advise the workmen to defer taking any hostile action until after the adjourned meeting.